Magnetoencephalographic responses correspond to individual annoyance of bandpass noise

The relation between human brain responses to an individual's annoyance of bandpass noise was investigated using magnetoencephalography (MEG) measurements and analysis by autocorrelation function (ACF) and cross-correlation function (CCF). Pure tone and bandpass noises with a centre frequency of 1000 Hz were used as source signals. The sound pressure level was constant at 74 dBA and the duration of the stimulus was 2.0 s. The scale values of annoyance for each subject were obtained by paired-comparison tests. In MEG measurements, the combination of a reference stimulus (pure tone) and test stimuli (bandpass noise) was alternately presented 30 times at a constant 2 s interstimulus interval. The results show that the effective duration of the ACF, τ_e, of MEG in the 8-13 Hz range, which represent repetitive features within the signal itself, became shorter during the presentation of an annoying stimulus. Also, the maximum value of the CCF, |φ(τ)|_max, became smaller. The shorter τ_e and smaller |φ(τ)|_max indicate that a wider area of the brain is unstable for longer with annoying auditory stimuli.     

LOUDNESS OF SHARPLY (2068 dB/OCTAVE) FILTERED NOISES IN RELATION TO THE FACTORS EXTRACTED FROM THE AUTOCORRELATION FUNCTION

This study examines the loudness of bandpass noises with center frequencies of 250, 500 and 1000Hz while changing the autocorrelation function (ACF). The bandwidth of the source signal was altered with a 2068 dB/octave sharp filter to control the ACF of the source signal. The scale values of loudness were obtained using a paired-comparison method. It is shown that the loudness of the bandpass noises inside the critical band is not constant. The loudness of the pure tone is greater than that of sharply filtered noises. The loudness of the bandpass noises increases with increasing effective duration of the ACF (τ_e) of the source signal.     

Semiconductor laser amplitude and phase noises effects in coherent optical frequency domain reflectometry C-OFDR

We study the effects of the semiconductor laser noise on the generated beat signal, in Coherent Optical Domain Reflectometry device. By using a general laser noise analytical model, based on Volterra non-linear treatment of laser rate equations, we find a novel general expression of the beat photocurrent. We show that the coherence and the incoherence cases are observed for a different delay time intervals than the ones known in literature. We show that the coherence domain corresponds to a delay time lower than the half of the laser coherence time τ₀<1/2τ_c, and the incoherence domain corresponds for τ₀>2τ_c. An original shape of the beat signal autocorrelation function affected by the laser noises is obtained.     

DIAGNOSTIC SYSTEM BASED ON THE HUMAN AUDITORY-BRAIN MODEL FOR MEASURING ENVIRONMENTAL NOISE—AN APPLICATION TO RAILWAY NOISE

Measurements of railway noise were conducted by use of a diagnostic system of regional environmental noise. The system is based on the model of the human auditory-brain system. The model consists of the interplay of autocorrelators and an interaural crosscorrelator acting on the pressure signals arriving at the ear entrances, and takes into account the specialization of left and right human cerebral hemispheres. Different kinds of railway noise were measured through binaural microphones of a dummy head. To characterize the railway noise, physical factors, extracted from the autocorrelation functions (ACF) and interaural crosscorrelation function (IACF) of binaural signals, were used. The factors extracted from ACF were (1) energy represented at the origin of the delay, Φ (0), (2) effective duration of the envelope of the normalized ACF, τe, (3) the delay time of the first peak, τ₁, and (4) its amplitude,ø₁ . The factors extracted from IACF were (5) IACC, (6) interaural delay time at which the IACC is defined, τ_IACC, and (7) width of the IACF at the τ_IACC,W_IACC . The factor Φ (0) can be represented as a geometrical mean of energies at both ears as listening level, LL.     

Numerical studies on wakefield excited by Gaussian-like microwave pulse in a plasma filled waveguide

Based on a differential equation derived analytically in terms of wakefield potential ?_MW in a plasma filled rectangular waveguide, we investigate the wakefield (E_MW) generated with the help of Gaussian-like microwave pulse under the effect of microwave frequency (f), pulse duration (τ), waveguide width (b), equilibrium plasma density (n₀) and microwave intensity (I). The study conducted for three cases of τ > 1/f_p, τ = 1/f_p and τ < 1/f_p, where f_p is the plasma frequency, reveals that the amplitude of the wakefield is increased for the large pulse duration and higher microwave intensity but is decreased with the waveguide width and microwave frequency for all these cases. The wakefield shows stronger dependence on the microwave frequency when the microwave with larger intensity is used. The wakefield decreases at a faster rate with the waveguide width for the case of τ > 1/f_p.     

Annoyance of noise stimuli in relation to the spatial factors extracted from the interaural cross-correlation function

While considering auditory-brain model for subjective responses, effects of spatial factors extracted from the interaural cross-correlation function (IACF) on annoyance of noise stimuli are examined. The previously developed indices to measure sound pressure levels (SPL) and frequency characteristics cannot fully explain the psychological effects of noise. In the first experiment, subjects judged their annoyance by changing fluctuations in the magnitude of interaural cross-correlation function (IACC) and the SPL. In the second, they judged their annoyance by changing fluctuations in the interaural time delay (τ_IACC) and the SPL. Results show that: (1) annoyance increased by increasing the fluctuations of IACC as well as the SPL, (2) annoyance increased by increasing the fluctuations of τ_IACC as well as the SPL.     

Effects of time delay on transient behavior of a time-delayed metastable system subjected to cross-correlated noises

The effects of time delay on the transient properties of a time-delayed metastable system subjected to cross-correlated noises are studied by means of a stochastic simulation method. It is found that: (i) Both additive noise and multiplicative noise can produce the noise enhanced stability (NES) effect; (ii) The time delay induces critical behavior on the NES, i.e., there is a critical value of the delay time τ_c1≈2.2, above which the time delay increases the stability of the system enhanced by the additive noise, and below which the NES effect induced by the additive noise disappears; (iii) There exists another critical value of the delay time τ_c2≈3.0, above which the time delay increases the stability of the system enhanced by the multiplicative noise and below which the time delay decreases it.     

Transient Raman gain stimulated by a noise pump

We predict a strong transient Raman gain stimulated by a Gaussian noise field in dispersive media. Our theory is based on the method of successive approximations, the first of which is the Markovian approximation. It is shown that the transient behavior will take place near critical pump intensity both for “short” (τ_p > T₂) and “ultrashort” (τ_p < T₂) laser pulses (τ_p is the pump pulse duration, T₂ is the relaxation time of optical phonons). Solutions for average intensities of the Stokes wave and optical phonons are obtained for arbitrary form of the given pump pulse. We show that transient Raman gain allows to form a very steep leading edge of the Stokes pulse.The steady-state increments of the second approximation describe the effects of a strong noise field. We show that after the intensity of the pump has exceeded a value beyond which the framework of validity of the Markovian approximation does not hold anymore, the steady-state Raman gain is saturated.We give a review of experimental results and make estimations for conditions of observing transient scattering in the field of a noise pump. Methods of obtaining the powerful femtosecond pulses based on stimulated Raman scattering of broad-band excimer lasers and supercontinuum emission are suggested.     

Characteristics of train noise in above-ground and underground stations with side and island platforms

Railway stations can be principally classified by their locations, i.e., above-ground or underground stations, and by their platform styles, i.e., side or island platforms. However, the effect of the architectural elements on the train noise in stations is not well understood. The aim of the present study is to determine the different acoustical characteristics of the train noise for each station style. The train noise was evaluated by (1) the A-weighted equivalent continuous sound pressure level (L_Aeq), (2) the amplitude of the maximum peak of the interaural cross-correlation function (IACC), (3) the delay time (τ₁) and amplitude (?₁) of the first maximum peak of the autocorrelation function. The IACC, τ₁ and ?₁ are related to the subjective diffuseness, pitch and pitch strength, respectively. Regarding the locations, the L_Aeq in the underground stations was 6.4 dB higher than that in the above-ground stations, and the pitch in the underground stations was higher and stronger. Regarding the platform styles, the L_Aeq on the side platforms was 3.3 dB higher than on the island platforms of the above-ground stations. For the underground stations, the L_Aeq on the island platforms was 3.3 dB higher than that on the side platforms when a train entered the station. The IACC on the island platforms of the above-ground stations was higher than that in the other stations.     

A STUDY OF THE BLENDING OF VOCAL MUSIC WITH THE SOUND FIELD BY DIFFERENT SINGING STYLES

The initial time delay Δt₁ between the direct sound and the first reflection and the subsequent reverberation time T_sub are usually fixed within a given space. Thus, concert halls do not have ideal conditions for all forms of music. It has been shown that the most preferred conditions for both listeners and performers are determined by the minimum value of the effective duration of the running autocorrelation function (ACF) of sound signals, (τ_e)_min. To determine the suitability of vocal music for a given sound field, (τ_e)_min of vocal music was analyzed, after recording five solo singers (tenor) in an anechoic room. The results showed that (τ_e)_min of the ACF of a voice source, which is closely related to the two temporal factors of the sound field, varies with singing style. A significant finding is that the values of (τ_e)_min of sound signals forfalsetto and medium falsetto are significantly longer than that for operatic singing.     

Stochastic resonance in an asymmetric bistable system with coloured noises and periodic rectangular signal

In this paper, we consider the phenomenon of stochastic resonance (SR) in an asymmetric bistable system with coloured noises and periodic rectangular signal. Expression of the signal-to-noise ratio (SNR) has been obtained under the adiabatic limit. We investigate the effect of any system parameter (such as p, q, r, τ₁, τ₂) on the SNR. The plot of SNR-τ₁ shows SR for some values of the additive noise self-correlation time τ₂, but not for the whole range of τ₂. The system bias r suppresses the SNR. When the intensity of additive noise q is increased, the SR phenomenon disappears in the plot of SNR-p, but the plot of SNR-q presents SR for almost all values of the multiplicative noise intensity p.     

Correlated Lvy flight in external force fields

The correlated Lvy flight is studied analytically in terms of the fractional Fokker-Planck equation and simulated numerically by using the Langevin equation,where the usual white Lvy noise is generalized to an Ornstein-Uhlenbeck Lvy process(OULP)with a correlation timeτc.We analyze firstly the stable behavior of OULP.The probability density function of Lvy flight particle driven by the OULP in a harmonic potential is exactly obtained,which is also a Lvy-type one withτc-dependence width;when the particle is bounded by a quartic potential,its stationary distribution has a bimodality shape and becomes noticeable with the increase of τc.     

The critical phenomenon and the re-entrance phenomenon in the anti-tumor model induced by the time delay

The effects of time delay τ on an anti-tumor model driven by a multiplicative noise and a periodic signal are investigated. The results obtained from the small delay approximation and numerical simulations indicate: (i) For the absence of the periodic signal in the system, the two-peak structure of the stationary probability distribution transforms into the single-peak structure with the increasing τ, and τ exists a critical value τc. For τ<τc, the stationary mean value 〈x〉_st of the cell population decreases as the noise intensity D increases, however, for τ>τc, the 〈x〉_st increases as the D increases; (ii) For the presence of the periodic signal in the system, the structure of the signal-to-noise ratio with changes of the D exhibits the transitions of one peak → two peaks → one peak as τ increases.     

Forming abilities of monatomic chains of several fcc and bcc metals in different crystallographic orientations

The forming abilities of monatomic chains (MC) of several fcc and bcc metals stretched in three principal crystallographic orientations of [1 1 1], [1 0 0] and [1 1 0] are analyzed in terms of a ratio between Peierls stress of a bulk crystal with dislocations (τ_p) and theoretical shear stress of a monatomic chain (τ_m). It is found that the structure and orientation dependent τ_m/τ_p values are proportional to the forming abilities of MC while τ_m/τ_p is a function of Possion's ratio ν. The above considerations are in agreement with known experimental and simulation results of Au. In addition, Nb as a candidate for MC formation is suggested.     

Noise destroys the coexisting of periodic orbits of a piecewise linear map

The effects of the Gaussian white noise and the Gaussian colored noise on the periodic orbits of period-5 (P-5) and period-6 (P-6) in their coexisting domain of a piecewise linear map are investigated numerically. The probability densities of some orbits are calculated. When the noise intensity is D=0.0001, only the orbits of P-5 exist, and the coexisting phenomenon is destroyed. On the other hand, the self-correlation time τ of the colored noise also affects the coexisting phenomenon. When τ_c<τ<τ_c', only the orbits of P-5 appear, and the stability of the orbits of P-5 is enhanced. However, when τ>τ_c' (τ_c and τ_c' are critical values), only the orbits of P-6 exist, and the stability of the orbits of P-6 is enhanced greatly. When τ<τ_c, the orbits of P-5 and P-6 coexist, but the stability of the orbits of P-5 is enhanced and that of P-6 is weakened with τ increasing.     

Associated relaxation time and the correlation function for a tumor cell growth system subjected to color noises

The associated relaxation time Tc and the normalized correlation function C(s) for a tumor cell growth system subjected to color noises are investigated. Using the Novikov theorem and Fox approach, the steady probability distribution is obtained. Based on them, the expressions of Tc and C(s) are derived by means of projection operator method, in which the effects of the memory kernels of the correlation function are taken into account. Performing the numerical computations, it is found: (1) With the cross-correlation intensity |λ|, the additive noise intensity α and the multiplicative noise self-correlation time τ₁ increasing, the tumor cell numbers can be restrained; And the cross-correlation time τ₃, the multiplicative noise intensity D can induce the tumor cell numbers increasing; However, the additive noise self-correlation time τ₂ cannot affect the tumor cell numbers; The relaxation time Tc is a stochastic resonant phenomenon, and the distribution curves exhibit a single-maximum structure with D increasing. (2) The cross-correlation strength λ weakens the related activity between two states of the tumor cell numbers at different time, and enhances the stability of the tumor cell growth system in the steady state; On the contrast, τ₁ and τ₃ enhance the related activity between two states at different time; However, τ₂ has no effect on the related activity between two states at different time.     

Beyond the pulse-area theorem: Role of the absorption and the dispersion in the propagation of weak ultrashort resonant pulses

We present here some fundamental but yet underlooked features of the propagation of weak ultrashort pulses (with Δ_dτ << 1, where Δ_d is the Doppler width and τ is the pulse duration) in resonant atomic media. We show that the pulse area behaviour and the pulse spectrum at resonance are governed by the usual optical depth (α₀L, where α₀ is the absorption coefficient at resonance and L the length of the medium), whereas the pertinent parameter that governs the severity of the dispersion effects and the distortion of the pulse is the dispersion parameter e_disp = (α₀L)Δ_dτ that we introduce. Paradoxical effect such as distortionless propagation (e.g. e_disp << 1) with vanishing pulse area (when α₀L >> 1) can then explained within this formalism.     

Effects of time-delay in stationary properties of a logistic growth model with correlated noises

A time-delayed tumor cell growth model with correlated noises is investigated. In the condition of small delay time, the stationary probability distribution is derived and the stationary mean value (〈x〉_st) and normalized varianceλ₂ of the tumor cell population and state transition rate (κ) between two steady states are numerically calculated. The results indicate that: (i) The delay time (τ) enhances the coherence resonance in 〈x〉_st as a function of the multiplicative noise intensity (D) and increases 〈x〉_st as a function of the additive noise intensity (α), i.e., τ enhances fluctuation of the system, however, the strength (λ) of correlations between multiplicative and additive noise plays a contrary role to τ on these; (ii) τ enhances the coherence resonance in κ as a function of D and increases κ as a function of α, i.e., τ speeds up the rate of state transition, however, λ also plays a contrary role to τ on these.     

Reorientational motion of acetone in solutions

Dipolar correlation functions of acetone in various solvents are obtained by Fourier transform of infrared spectra. The analysis of the shapes of correlation functions shows that the reorientational process is diffusional in the time scale longer than about 0.3 × 10^?12 sec. In nonpolar solvents the ratios of correlation times τ_A : τ_B : τ_C do not vary in different solvents, and the reorientation around b axis is more restricted than around the other axis. The length of correlation time is dependent on the density of solvent rather than the viscosity. These observations are unexpected if only the electrostatic interaction is considered. In polar solvents correlation times are longer than in nonpolar solvents and the tendency is especially remarkable in τ_B. An electrostatic interaction between polar molecules seems to be responsible for these observations. The solvent effect on the frequency shifts of carbonyl stretching vibration is consistent with the result of correlation times.     

Effects of time delay and non-Gaussian noise on the dynamics of a perceptual bistability

In this paper, we investigate the effects of time delay and non-Gaussian noise on the dynamics properties of the attractor network model of perceptual bistability. Using delay Fokker–Planck equation and projection operator method, the stationary probability distribution P_st(x), the associated relaxation time T_c, and the normalized correlation function C(s) for perceptual bistability are obtained, respectively. Research results show that: (i) the time delay τ and the correlation time τ₀ from non-Gaussian noise can induce the change of the peaks in the P_st(x), i.e., the transition of the system appears; (ii) there exhibits an optimal value of the τ₀ or τ by which the T_c or C(s) is maximum, this maximum shows the τ₀ or τ first reduces the stability of the attractor network model of perceptual bistability in the steady state, and then enhances it; and (iii) the noise intensity P or departure q from the Gaussian noise only enhances the stability of the attractor network model of perceptual bistability in the steady state.